1. Field of the Invention
The present invention relates to digital telephone offices and more particularly to an arrangement using standardized line circuits in such telephone offices. The specialized analog circuitry portion is separated from the various line circuits and connected to an analog access network which provides concentration and access to subscriber stations.
2. Description of the Prior Art
Line circuits for digital telephone offices are of a hybrid nature in that they use analog circuitry for interfacing to the various subscriber stations and they use Pulse Code Modulation (PCM) circuitry for interfacing to the digital network of the digital telephone office. These line circuits are complex and expensive, and numerous varieties of them are required to operate with the numerous types of subscriber equipment, such as party lines, coin telephones, etc. Every line circuit requires loop status circuitry, and PCM processing circuitry, but coin detection circuitry, and party line circuitry need not be dedicated to each line circuit. Therefore, by separating the analog line circuitry from the various line circuits, a standardized line circuit can be used for all subscriber stations and the complex and expensive specialized analog line circuitry can be concentrated and provided access to the subscriber stations via an analog network.
Accordingly, it is the object of the present invention to provide a novel arrangement for separating specialized analog line circuitry from line circuits used in digital telephone offices, so that a standardized digital line circuit can be used for all subscriber stations.